The multilayer networks mentioned above can be generalized to allow for the modeling of
more than one property of the nodes in each layer. Therefore, we define a sequence
\(\lbrace L_j\rbrace _{j=1}^{d}\)  of sets of layers with \(d\)  being the number of different properties
that one would like to model; \(L_j\)  is the set of layers for the property \(j\) .
Then \(V_L=V\times L_1\times \ldots \times L_d\)  and the nodes are identified as
\(v_i^{\ell _1,\ldots ,\ell _d}\) . For more details on this kind of generalization, we refer
to [1]}, [2]} and the references therein, where general frameworks for multilayer
network are discussed together with their mathematical formulation.
